Recognizing and Intervening in Pituitary Apoplexy

Elizabeth Zink, MS, ACNP, CCRN, CNRN

Disclosures

Topics in Advanced Practice Nursing eJournal. 2005;5(4) 

In This Article

Review of the Anatomy and Physiology of the Pituitary Gland

The adult pituitary gland weighs approximately 500-600 g and is typically 1.2-1.5 cm in diameter and 0.5 cm thick, occupying approximately 80% of the sellar space.[1] The pituitary gland is connected to the hypothalamus by the infundibulum, or pituitary stalk, and is seated within the sella turcica in the skull base and surrounded by the sphenoid bones on either side. Understanding the anatomic structure and location of the pituitary and surrounding structures is essential to understanding mechanisms of infarction and hemorrhage in the gland.

The pituitary gland consists of anterior and posterior lobes connected by a middle, intermediate lobe (Figure 3). The anterior lobe, or adenohypophysis, produces and secretes 6 hormones essential for metabolic function throughout the body ( Table 1 ). The posterior lobe, the neurohypophysis, produces and secretes 2 hormones: antidiuretic hormone and oxytocin. The neurohypophysis arises from the hypothalamus during fetal development. Anterior and posterior lobes are separated by a section of avascular tissue called the pars intermedius or intermediate lobe. The pars intermedius was originally thought not to function in humans; however, some have suggested that this portion of the pituitary plays a role in producing hormone precursors and a small amount of melanocyte-stimulating hormone.

Figure 3.

Structure of the pituitary gland. Reproduced with permission of publisher from Melmed S: V Pituitary. 3 Endocrinology. ACP Medicine Online. Dale DC, Federman DD, Eds. WebMD Inc., New York, 2004. http://www.acpmedicine.com

Secretion of pituitary hormones is controlled by the hypothalamus through a negative feedback system. The hypothalamus produces and secretes releasing and inhibitory hormones that are delivered to the anterior pituitary gland through an arterial vascular system called the hypothalamic-hypophysial portal system. By contrast, the hypothalamus delivers neuronal impulses directly to the tissue of the posterior pituitary gland. These impulses control the release or inhibition of hormones produced in that lobe.[2]

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